Valves of the above type are known which substantially comprise an outer casing defining a water flow cavity; a disk-shaped base member, which is inserted hermetically inside the cavity, and defines an intermediate opening section permitting water flow between a first and a second chamber of the cavity separated by the base member; and a flexible shutter having a stem fitted coaxially through the base member, and a membrane portion which projects radially from the end of the stem facing the first chamber, and cooperates elastically, by virtue of fluid pressure, with the opening section to separate the first and second chamber hermetically.
Valves of the above type are normally used to permit one-way water flow, and, in particular, are maintained in a closed configuration when the pressure in the first chamber is greater than that in the second chamber.